This invention relates to a screwdown in the form of an assembly for removable use as an integral component of a rolling mill to adjust the gap between a pair of processing rolls, and more particularly to such a screwdown embodying a construction and arrangement of parts to occupy a minimum of space within the windows of the mill housings while supported by the housings to transmit rolling forces from the roll positioned thereby to the mill housing.
As is well known in the rolling mill art, a screwdown is the mechanical system in a rolling mill used to adjust the gap between processing rolls for workpieces. Bars, billets, rods and similar workpieces are usually processed in a 2-high rolling mill after the gap between the rolls is established by operating the screwdown. Because of the nature of the rolling operation, it is usually unnecessary to operate the screwdown while the rolls engage the workpiece. A manually-operated screwdown is suitable for positioning one roll relative to the other in the absence of a rolling load; thus eliminating the need for massive and expensive motors.
A more economical rolling mill design is desired to minimize the capital investment required for rolling mills to process such workpieces. In a conventional rolling mill, the screwdown takes the form of screws threadedly received in nuts which are received in openings formed in the tops of the mill housings. One characteristic of a cast mill housing is the thickened or protruding areas at the top portion thereof to accommodate the rolling forces and provide support for the screwdown nut. The casting and machining operations require time, facilities and expenses, representative of a substantial cost to form cast mill housings. This cost can be minimized by an alternative fabrication procedure. A thick metal plate is usable after only machining operations to provide mill housings the necessary window openings and the like. Housings from metal plates are economically produced and capable of withstanding greater rolling loads with less weight.
Conventional screwdowns are costly both from the standpoint of the capital investment and necessary servicing operations, particularly mill downtime for servicing the screwdowns. When the screws for the screwdown extend through the tops of the mill housings, it is a time-consuming and laborious operation to remove each screw and/or nut from the bored openings in the housing tops. Efforts in the past to alleviate the problems associated with screwdowns in the tops of mill housings include the concept of interposing wedges between the top roll chock and the mill housing. By adjusting the position of one wedge with respect to the other within each housing window, the top roll assembly is moved toward or away from the lower roll assembly. However, such wedges are not an acceptable substitute for screwdowns, particularly because the relative position of one wedge with respect to the other and synchronous movement between the wedges are not sufficiently controllable. The rolling force transmitted by the wedges is translated into a lateral displacement component force acting on one or both of the wedges. Moreover, severe restrictions occur as to the distance through which adjustment of the rolls relative to each other can occur. These shortcomings, together with the excessive demands for lubrication and other maintenance, render the concept of wedges unsuitable for use in such rolling mills. To alleviate these and other problems arising out of the need for apparatus to adjust the position of one roll relative to another roll in the rolling mill, the present invention provides readily-servicable and independent screwdown assemblies for support wholly within the window of each mill housing of the rolling mill.